Avago Technologies 3ware SAS 9750-4i User Manual
Page 107
Unit Object Commands
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disks, the default grouping is 5, and for 12 disks, the disks can be grouped into
groups of 3, 4, or 6 drives (the group of 4 drives is set by default as it provides
the best of net capacity and performance). For 15 disks, the disks can be
grouped into groups of 5 drives (3 drive groups would make 5 subunits, you
can have a maximum of 4 subunits). For 16 disks, the disks can be grouped
into groups of 4 or 8 drives.
Note that RAID-10 always has group=2, so an attribute specifying it’s group
is not necessary.
stripe=size consists of the stripe size to be used. The following table
illustrates the supported and applicable stripes on the respective unit types and
controller models. Stripe size units are in KB (kilobytes).
noscan attribute instructs CLI not to notify the operating system of the
creation of the new unit. By default CLI will inform the operating system.
One application of this feature is to prevent the operating system from
creating block special devices such as /dev/sdb and /dev/sdc as some
implementations might create naming fragmentation and a moving target.
nocache attribute instructs CLI to disable the write cache on the migrated
unit. Enabling write cache increases write performance but at the cost of
potential data loss in case of sudden power loss (unless a BBU or UPS is
installed). By default the cache is enabled. To avoid the possibility of data loss
in the event of a sudden power loss, it is recommended not to set nocache
unless there is a BBU (battery backup unit) or UPS (uninterruptible power
supply) installed.
Table 14: Supported Stripe Sizes
Model
R0
R1
R5
R6
R10
Spare
R50
Single
7/8000
64
N/A
64
N/A
64
N/A
N/A
N/A
128
128
256
256
512
512
1024
1024
9000
a
a. Models 9500S, 9550SX, and 9590SE
16
N/A
16
N/A
16
N/A
16
N/A
64
64
N/A
64
64
256
256
N/A
256
256
9750,
9690SA,
and
9650SE
16
N/A
16
16
N/A
16
N/A
64
64
64
64
64
256
256
256
256
256